Method and apparatus for compression molding closure liners

ABSTRACT

A method and apparatus for compression molding closure liners wherein a set of tooling including a first assembly and second assembly which are movable toward and away from one another. The first assembly of tooling has a liner forming member and a closure engaging sleeve thereon and the second assembly has a closure supporting pad thereon. A cam is associated with the first assembly of tooling for moving the closure engaging sleeve into engagement with a closure and the liner forming member into position for compression molding a charge of plastic extrudate in the closure when it is supported on the closure supporting pad. A gas cylinder is associated with the closure supporting pad providing a predetermined controlled pressure that determines the compression molding force on the plastic. In a preferred mode, a plurality of sets of tooling are provided in circumferentially spaced relation to one another on a turret.

This invention relates to compression molding of liners in closures.

BACKGROUND AND SUMMARY OF THE INVENTION

In forming liners in closures, it has been common to compression moldthe liner. Typical patents showing such a method and apparatus are U.S.Pat. Nos. 2,072,536, 2,930,081, 3,827,843, 4,274,822, 4,312,824 and4,497,765.

One of the problems in compression molding of liners is that ofcontrolling the molding force when molding liners directly into aclosure such that sufficient molding force is used to fill the requiredseal volume and not produce shorts and, at the same time, to limit thissame force to avoid flashing of the liner. This force should beconsistent and equal on each of all toolings to avoid processvariability. The use of compression springs to control this force wouldnot be consistent from tool to tool due to the variability of the ratingof the springs and due to the inevitable fatigue that would be inducedafter substantial length of running. Further, means to readily adjustthe molding force of all toolings with one adjustment of system pressureis desirable.

Among the objectives of the present invention are to provide a methodand apparatus for compression molding liners in plastic closures whereinthe molding pressure on the charge that is being shaped to define theliner is accurately controlled; wherein when an array of tooling isprovided, each set of tooling functions independently of the other;wherein the forming pressure can be readily changed; and wherein thetooling can be readily assembled and removed.

In accordance with the invention, the method and apparatus forcompression molding closure liners includes providing a first assemblyand second assembly which are movable toward and away from one another.The first assembly of tooling includes a liner forming member, a closureengaging sleeve thereon, and the second assembly has a closuresupporting pad thereon. A cam is associated with the first assembly oftooling for moving the closure engaging sleeve into engagement with aclosure and the liner forming member into position for compressionmolding a charge of plastic extrudate in the closure when it issupported on the closure supporting pad. A gas cylinder is associatedwith the closure supporting pad containing gas at a predeterminedpressure providing a controlled molding pressure on the plastic. In apreferred mode, a plurality of sets of tooling are provided incircumferentially spaced relation to one another. Means are provided forreadily changing the pressure.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of an apparatus embodying theinvention.

FIG. 2 is a top plan view, parts being broken away.

FIG. 3 is a fragmentary vertical sectional view through a portion of theapparatus.

FIG. 4 is a fragmentary plan view taken along the line 4--4 in FIG. 3.

FIG. 5 is a fragmentary sectional view on an enlarged scale of a firstor upper assembly of tooling shown in FIG. 3.

FIG. 6 is a fragmentary vertical sectional view on an enlarged scale ofa second or lower assembly of tooling shown in FIG. 3.

FIG. 7 is a plan view of a nitrogen manifold utilized in the apparatus.

FIG. 8 is a sectional view taken along the line 8--8 in FIG. 7.

FIG. 9 is a sectional view taken along at the circle 9--9 in FIG. 8.

FIG. 10 is a fragmentary sectional view taken along the line 10--10 inFIG. 7.

FIG. 11 is a fragmentary sectional view taken along the line 11--11 inFIG. 7.

FIG. 12 is a fragmentary sectional view taken along the line 12--12 inFIG. 7.

FIG. 13 is a fragmentary side elevational view of cams utilized in theapparatus.

FIG. 14A is a fragmentary view of the upper cam shown in FIG. 13.

FIG. 14B is a view of the lower cam shown in FIG. 13.

FIG. 15 is a fragmentary plan view of a portion of the apparatus shownin FIG. 1.

DESCRIPTION

Referring to FIGS. 1-3, the apparatus embodying the invention comprisesa base 30 on which a column 31 is fixed. A carousel or turret 32 isrotatably mounted on column 31 by upper and lower bearings 33, 34. Theturret 32 supports sets of tooling comprising a first or upper assembly35 of tooling and a second or lower assembly 36 of toolingcircumferentially spaced about the turret 32. An annular fixed cam 37 isprovided and is associated with the first assembly 35 of tooling, aspresently described. Each second assembly 36 of tooling further includesan annular gas manifold 38 that supports a plurality ofcircumferentially spaced gas cylinders 39. Piston 40 of gas cylinder 39acts against a closure supporting pad 41 in the lower or second set oftooling 36 through an intermediate member 42 (FIG. 7). The manifold 38and gas cylinders 39 are charged with an atmospheric gas, preferablynitrogen, at predetermined pressure.

Referring to FIGS. 5 and 6, each first assembly 35 of tooling comprisesan annular support 50. An actuator 51 is movable vertically in support50 by engagement with a cam follower roller 52 on the actuator 51 withcam 37 to move a liner forming plunger assembly 53 mounted on theactuator 51 downwardly through a fixed stroke. A closure engaging sleeve54 is provided about the liner forming tool 53 and is yieldingly urgedaxially outwardly and downwardly by circumferentially spaced springs 55engaging pins 56. A flange 57 on the tooling limits the outward movementby engagement with a flange 58 on an outer fixed sleeve 59.

Coolant is provided to the interior of the liner forming plunger 53 andcirculated therethrough through inlet 60 and outlet 61 connected, inturn, to a distributor 63 mounted rotatably in the column 31 and rotatedby a gear 64 such that the distributor and associated hoses, not shown,move with each set of tooling 35 (FIG. 3).

Referring to FIGS. 3 and 5, the closure supporting pads 41 are mountedin a support ring 70 that, in turn, is mounted on a radial flange 71 onthe turret 32. The support ring 70 is secured to flange 71 by bolts 72.The annular support 50 for the first assemblies 35 is supported on thesupport ring 70 by bolts 73 (FIGS. 5, 7).

Referring to FIGS. 3 and 6, annular gas manifold 38 is mounted on theunderside of support ring 70 by bolts 75. The gas cylinders 39 aremounted on the gas manifold 38 and extend into cylindrical openings 76that extend downwardly. Each gas cylinder 39 has an annular flange 77that engages the upper surface of gas manifold 38 and cooperatestherewith to form a seal. The piston 40 of each cylinder 39 engages anintermediate member 78 which, in turn, engages the closure support pad41. A light spring 79 urges the pad 41 upwardly to facilitate loading ofa closure C in position on the pad 41. A retaining ring 80 held inposition by bolts 80a limits the upward movement of the pad 41.

Referring to FIGS. 7-12, gas manifold 38 has an inlet 81 with anassociated one-way valve 82 (FIG. 12). The chambers 76a of openings 76beneath each gas cylinder 38 (FIG. 6) are interconnected by passages83-85 to provide a manifold chamber in the chambers 76a beneath thecylinders. The manifold chamber is provided with nitrogen at apredetermined high pressure thereby defining a manifold chamber 76abeneath each gas cylinder 39 which is at the predetermined pressure. Thepassages 84, 85 provide communication to chamber 76a.

One or more of the chambers 76a can be provided with a pressure gauge 86(FIG. 10) or a rupture disk 87 for pressure relief (FIGS. 8, 9 and 11).

Referring to FIGS. 14A and 14B, cam 37 is positioned to lower the uppertooling 35 into position by engagement of the roller 52 on the uppertooling 35 for compressing the liner. A second cam 85 is provided forengaging a second roller 86 on actuator 51 (FIG. 5) to lift the uppertooling in order to facilitate placement and removal of closures on theclosure supporting pads 41.

The closures C are preferably made of plastic such as polypropylene orpolyethylene and comprise a base wall and a peripheral skirt. A typicalclosure is such as shown in U.S. patent application Ser. No. 07/920,931filed Jul. 28, 1992, now U.S. Pat. No. 5,265,747, incorporated herein byreference.

In operation, charges of molten plastic are fed successively to eachclosure C positioned in inverted position as it is moved through a worm90 and starwheel 91. The charge of extrudate of plastic material forforming the liner may be delivered to each closure when the closure isin any position either before it enters the turret 32 or after it hasentered the turret 32.

As the closure C is moved by supporting pad 41 between the first orupper assembly 35 of tooling and the lower assembly 36 of tooling whichsupports the closure and turret 32 is rotated, the cam 37 moves theupper tooling 35 downwardly causing the sleeve 53 to engage the closureC and then move the liner forming plunger 53 downwardly through a fixedstroke to compress the charge of plastic into a liner. After the initialcompression of the light spring 79, the control of the forming pressureis through the predetermined pressure on the piston rod 40 of the gascylinder 39.

Inasmuch as the pressure of the gas cylinder 39 is at a very highpressure, for example, on the order to 850 p.s.i., and the amount ofmovement is very small on the order of 0.020 in., the volume of glassdisplaced relative to the total volume of the system is relativelyinsignificant. The gas volume of the manifold is thereby substantiallyconstant and the force generated by each cylinder is substantiallyconstant. Accordingly, the forming or compression force on the charge ofplastic is accurately controlled at a predetermined pressure.

After a predetermined portion of the cycle of application of a very highpressure, the cam 37 has a rise that allows the upper tool formingplunger 53 to retract sufficiently to raise the lower support plate 41until the support plate 41 contacts the shoulder and the support pad 51and is supported only by the spring 79. During this stage, the moldingforce is reduced during the plastic cure.

Furthermore, it is possible to adjust the pressure in the manifold byincreasing or decreasing the pressure through the inlet valve 81.

It can thus be seen that in accordance with the invention, the controlof mold forces within each set of compression molding tool, isindependent of external compensating means.

The turret or carousel is mounted on heavy duty taper roller bearings toadequately withstand the cantilevered loading of the molding force. Thegas manifold 38 has cross drillings 83-85 in place to connect all thecylinders 39 to a common chamber and to a common charging port forsystem pressure setting.

The upper tooling ring 50 is attached to the turret and has bushings toguide each upper tooling assembly 35 in the form of a cartridge and itsassociated inner tooling components as it is actuated downwardly by thecam roller 52 engaging the upper cam 37 (FIGS. 13, 14A and 14B). Theinner tooling components include a spring loaded outer toolingcomponents including a spring loaded outer sleeve and a directlyactuated inner tooling. The upper tooling cam 37 is continuous, and withno moving sections. As the turret 32 rotates, successive sets of uppertooling are actuated downwardly toward the closure as it rests on thelower tooling plate, and the outer sleeve engages the closure seal ringand begins to compress the springs. The previously introduced extrudedpellet in the closure is formed by the advancing inner plunger 53, andeach inner tooling continues to advance a common fixed stroke. Theadvancing inner plunger creates a pressure within the melt, and this inturn results in a force transmitted to the load plate 41, which thencompresses the spring until the piston rod is engaged. The gas cylinder39 resists the force of molding until the preset limiting force isachieved, whereby the cylinder compresses to limit the molding force.The inner plunger continues to complete its fixed stroke, and duringthis time the mold force remains at its limiting force as preset by thegas pressure.

To offload the tooling forces after molding, the upper cam has a rise,for example, of about 0.040 in., and this allows the upper tool toretract sufficiently to raise the supporting pad 41 and the load plateuntil the intermediate plate 70 contacts the shoulder in the toolingring, and the tooling plate is supported only by the spring. Thus duringthe curing stage, the molding force is reduced. As indicated above, thecantilevered load on the turret is opposed by the tapered roller bearingmount of the turret.

It can thus be seen that there has been provided a method and apparatusfor compression molding liners in plastic closures wherein the moldingpressure on the charge that is being shaped to define the liner isaccurately controlled; wherein when an array of tooling is provided,each set of tooling functions independently of the other; wherein theforming pressure can be readily changed; and wherein the tooling can bereadily assembled and removed.

I claim:
 1. A method for compression molding liners in closures having abase wall and a peripheral skirt comprisingproviding a first set oftooling including a first assembly having a liner forming plunger, afirst sleeve surrounding the plunger and a closure engaging sleevesurrounding the first sleeve, and a second assembly including a closuresupporting pad, providing a cam for moving the liner forming plungertoward the closure supporting pad, providing a gas cylinder having a gaspressure chamber and including a piston operable on with one of saidclosure supporting pad and said liner forming plunger, positioning aclosure on the closure supporting pad, delivering a charge of extrudateof plastic material into the closure, causing the cam to move theclosure engaging sleeve into engagement with the closure and the linerforming plunger through a fixed stroke within the closure to compressthe charge and form a liner, and controlling the compression moldingforce by the magnitude of pressure within the gas cylinder.
 2. Themethod set forth in claim 1 wherein the step of providing a gas cylindercomprises positioning the gas cylinder beneath the closure supportingpad.
 3. The method set forth in any one of claims 1 or 2 wherein saidstep of providing a gas cylinder includes providing a predeterminedpressure in said gas cylinder.
 4. The method set forth in any one ofclaims 1, 2 or 3 including providing an array of said sets of toolingincluding first assemblies and second assemblies and including said gascylinders,moving said sets of tooling successively in an endless pathpast a station wherein a charge of extrudate is delivered successivelyto a closure on the supporting pad of each second assembly, andthereafter moving said sets of tooling relatively and successively suchthat said cam causes a liner to be formed in each closure and therespective gas cylinder controls the compression force.
 5. The methodset forth in claim 5 including the step of interconnecting the gaschambers of said gas cylinders.
 6. The method set forth in claim 5wherein said step of interconnecting cylinders comprises providing amanifold communicating with said gas chambers.
 7. The method set forthin claim 6 including the step of supporting said cylinders in saidmanifold.
 8. The method set forth in claim 7 including the step ofsupplying gas to said manifold at a predetermined pressure.
 9. Anapparatus for forming a liner in a closure comprisinga set of toolingcomprising a first assembly including a liner forming plunger, a firstsleeve surrounding the plunger, and a closure engaging sleevesurrounding said first sleeve, a second assembly including a closuresupporting pad for supporting a closure in position with respect to thefirst assembly, a gas cylinder having a gas pressure chamber and apiston operable on one of said closure supporting pad and said linerforming plunger, a cam for moving the first assembly toward the closuresupporting pad and the closure engaging sleeve into engagement with aclosure on the pad and the liner forming plunger within the closurethrough a fixed stroke to form a liner, and means for providing gas at apredetermined pressure into the gas chamber of said cylinder such thatthe compression molding force is established by the pressure of gaswithin the cylinder.
 10. The apparatus set forth in claim 9 wherein saidgas cylinder is provided beneath the closure supporting pad.
 11. Theapparatus set forth in any one of claims 9 or 10 including an array ofsaid sets of tooling including a first assembly, a second assembly andsaid gas cylinders,means for moving said sets of tooling in an endlesspath past a station wherein a charge of extrudate can be delivered to aclosure on the supporting pad of each second assembly and thereafter formoving each set of tooling to a position said cam for moving said firstassemblies to form a liner.
 12. The apparatus set forth in claim 9including means interconnecting said gas chambers of said gas cylinders.13. The apparatus set forth in claim 12 wherein said meansinterconnecting said gas cylinders comprises an annular manifold andmeans supporting each gas cylinder in position such that the gas chamberof each gas cylinder communicates with said manifold.
 14. The apparatusset forth in claim 13 wherein said manifold includes a charging valvethrough which the predetermined gas pressure in said manifold can beprovided.
 15. The apparatus set forth in claim 14 wherein said manifoldcomprises a plurality of circumferentially spaced generally cylindricalchambers into which gas cylinders extend and interconnecting passages insaid manifold extending between said cylindrical chambers.
 16. Theapparatus set forth in any one of claims 12-15 wherein said secondassemblies comprise a first annular ring, said closure supporting padsbeing supported on said ring.
 17. The apparatus set forth in claim 16wherein said first assemblies comprise a second annular ring in whichsaid first assemblies are supported.
 18. The apparatus set forth inclaim 17 wherein said second annular ring is supported on said firstannular ring.
 19. The apparatus set forth in claim 18 wherein said firstannular ring is mounted on a rotatable turret.
 20. The apparatus setforth in claim 19 wherein said second ring includes an array of verticalopenings in which said first sets of tooling are supported such thatthey can be inserted and removed by vertical movement downwardly andupwardly relative to the second annular ring.
 21. The apparatus setforth in claim 20 including a second cam positioned for engaging thefirst set of tooling to lift the plunger when each second assembly isadjacent the station for delivery of a charge of extrudate.
 22. Themethod set forth in claim 2 including providing a second cam for movingthe liner forming plunger when said second assembly is in position forthe step of receiving a charge of extrudate into the closure.
 23. Themethod set forth in claim 4 including providing a second cam forengaging each said liner forming plunger to lift the plunger when eachsecond assembly is in position for receiving a charge of extrudate intothe closure.
 24. The apparatus set forth in claim 10 including a secondcam for moving the liner forming plunger when said second assembly is inposition for receiving a charge of extrudate into a closure.
 25. Theapparatus set forth in claim 21 wherein said first assembly comprises anannular support, an actuator movable vertically in said support byengagement with said first cam, a closure engaging sleeve provided onsaid actuator about said plunger and a flange on said plunger and aninterengaging flange on said closure engaging sleeve limiting axialoutward movement of said plunger.
 26. The apparatus set forth in claim21 wherein each said first assembly comprises an annular support, anactuator movable vertically in said support by engagement with saidfirst cam, a closure engaging sleeve provided on said actuator aboutsaid plunger and a flange on said plunger and an interengaging flange onsaid closure engaging sleeve limiting axial outward movement of saidplunger.
 27. The apparatus set forth in claim 21 including means forproviding coolant to the liner forming plunger.
 28. The apparatus setforth in claims 10 wherein said closure supporting pad is supported onan intermediate member, said cylinder having an annular flange engagingsaid support and a piston engaging said intermediate member and a springinterposed between said pad and said intermediate member urging said padupwardly.
 29. The apparatus set forth in claim 11 wherein each saidclosure supporting pad is supported on an intermediate member, saidcylinder having an annular flange engaging said support and a pistonengaging said intermediate member and a spring interposed between saidpad and said intermediate member urging said pad upwardly.